Horology & Navigation: How to Find True North Using Your Watch… Kind of

Any analog watch can be used as a rough compass. Here’s how…

First, with your watch held level in front of you, find the sun in the sky and turn your watch so that the hour hand is pointing directly toward the sun (please don’t look directly at the sun!). Then, splice an imaginary line between the hour hand and the 12 o’clock mark. That imaginary line is pointing south, and the opposite projection of that line therefore points north. Viola!

The basic principle of this method is based on the fact that 12 noon is when the sun is at its highest point.

Although, this method only works for the northern hemisphere. For the southern hemisphere, rather than pointing the hour hand at the sun, point the 12 o’clock marker towards the sun, then find south by splitting the angle with the hour hand like before. 

During Daylight Savings time, be sure to use the watch’s 1 o’clock position rather than 12 o’clock. Also note that in the AM, you’ll have to split the middle of the hour hand and 12 o’clock by moving clockwise across the dial, and anti-clockwise in the PM. 

So with all of that being said, it’s perhaps best to use a trusty compass!

However some watches feature clever dial markings and simple complications (such as an additional hand) to make using your watch as a compass easier. However, an inaccuracy in the above method, and therefore with these specialist watches also, is that a watch keeps track of mean solar time, not true solar time. Mean solar time is the time within a particular time-zone, while true solar time is the time specific to that place. Take GMT: when in Greenwich, London, on a sunny day, the sun is at its highest point at 12 noon. But in the same timezone over in Bristol, some 100 miles to the West of the meridian line, the sun is past its highest point, but it remains to be 12 noon. Therefore, when using your watch as a compass when far away from the point of mean time (Greenwich in the case of GMT; ±0hrs), there is a window of error when using your watch as a compass. 

The Arnold & Son True North Perpetual (above, second from the left) solves this by keeping track of solar time as well as mean time, but that’s a subject for a whole new post. 

For now, happy exploring!